title: Adult-onset asthma becomes the dominant phenotype among women by age 40 years. the longitudinal CARDIA study.
abstract: BACKGROUND
  Although asthma is usually considered to originate in childhood, adult-onset disease is being increasingly reported.
  
  
  OBJECTIVE
  To contrast the proportion and natural history of adult-onset versus pediatric-onset asthma in a community-based cohort. We hypothesized that asthma in women is predominantly of adult onset rather than of pediatric onset.
  
  
  METHODS
  This study used data from the Coronary Artery Risk Development in Young Adults (CARDIA) cohort in the United States over a 25-year period. Adult- and pediatric-onset asthma phenotypes were studied, as defined by age at onset of 18 years or older. Subjects with asthma were categorized by sex, obesity, atopy, smoking, and race by mean age/examination year, using a three-way analysis of covariance model. Natural history of disease was examined using probabilities derived from a Markov chain model.
  
  
  RESULTS
  Asthma of adult onset became the dominant (i.e., exceeded 50%) phenotype in women by age 40 years. The age by which adult-onset asthma became the dominant phenotype was further lowered for obese, nonatopic, ever-smoking, or white women. The prevalence trend with increasing time for adult-onset disease was greater among subjects with nonatopic than atopic asthma among both sexes. Furthermore, adult-onset asthma had remarkable sex-related differences in risk factors. In both sexes, the quiescent state for adult-onset asthma was less frequent and also "less stable" over time than for pediatric-onset asthma.
  
  
  CONCLUSIONS
  Using a large national cohort, this study challenges the dictum that most asthma in adults originates in childhood. Studies of the differences between pediatric- and adult-onset asthma may provide greater insight into the phenotypic heterogeneity of asthma.
authors.affiliation: University of New Mexico Health Sciences Center School of Medicine, Department of Medicine, Albuquerque, NM 87131, USA. asood@salud.unm.edu
authors.forename: Akshay
authors.initials: A
authors.lastname: Sood
authors.forename: Clifford
authors.initials: C
authors.lastname: Qualls
authors.forename: Mark
authors.initials: M
authors.lastname: Schuyler
authors.forename: Alexander
authors.initials: A
authors.lastname: Arynchyn
authors.forename: Jesse H
authors.initials: JH
authors.lastname: Alvarado
authors.forename: Lewis J
authors.initials: LJ
authors.lastname: Smith
authors.forename: David R
authors.initials: DR
authors.lastname: Jacobs
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D017668:Age of Onset; D001249:Asthma / Q000453:epidemiology*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D015994:Incidence; D010641:Phenotype; D011159:Population Surveillance; D012189:Retrospective Studies; D014481:United States / Q000453:epidemiology; D055815:Young Adult